Geek Answers: Why does time seem to slow down in moments of extreme danger?

To really alter the flow of time, you have to be going very, very fast — close to the speed of light. Being creatures of squishy organic matter, we lack the ingrained machine-like precision to objectively measure time. So even though time is always moving at roughly the same rate for us, sometimes it seems to be going slower or faster. Perhaps the clearest example of this effect is in those harrowing moments when life throws you a curve ball.

Maybe your tires slip on an an icy road, or you stumble going down the stairs. When something goes wrong, it’s common to hear someone later claim that time slowed down. It’s something many of us can relate to, but what causes it?

You can construct a reasonable-sounding rationale for the slowed perception of time during times of crisis. If you’re in danger, it would be very advantageous to have more time to react. Could evolution have shaped our reactions to give us that edge? Does the brain actually kick into high gear when we’re in danger?

David Eagleman, an author and Assistant Professor of neuroscience and psychology at Baylor College of Medicine decided to find out a few years ago. Eagleman began searching for a way to induce the deep seated fear for one’s life that seemed to trigger the perceived slowing of time. It turned out it’s harder to do than you might think. An unexpected, but ultimately uneventful trip and fall could certainly do it, but a thrilling rollercoaster couldn’t. If a test subject knew they weren’t in danger, they didn’t experience time any differently. The researchers needed something safe, yet utterly terrifying.

Eagleman eventually discovered Suspended Catch Air Device (SCAD) diving. Essentially, you are dangled from the top of a 150-foot tower and dropped. As you rocket downward in the sweet embrace of gravity, a loose rope system tightens on the harness you were strapped into prior to the drop. The ropes will (ideally) catch you before you slam into the ground. This is a sufficiently frightening experience that it gives people that feeling of time standing still.

So how did Eagleman utilize SCAD diving to figure out what’s going on in that eternal moment? The researchers attached a device to the test subjects’ wrists called a perceptual chronometer — a watch that flashed numbers on a display too quickly for a person to read normally. The thought was that if the perception of time was actually slowing down in free fall, subjects should have been able to read the numbers on the watch. Eagleman and his team found that, no, people can’t actually see things happening in slow motion.

From this result, researchers realized that time was not actually being perceived any differently in the moment. However, when asked how long the fall took, people invariable overestimated by huge margins. Something was causing people to experience time at a different rate, but there was no evidence of it during the fall.

Eagleman eventually determined the slowed time effect is not a trick of perception while falling, but of your memory after it’s over. When you encounter something sufficiently startling or frightening, a pair of structures in the brain known as the amygdalae shift into overdrive. The amygdalae are responsible for processing short-term memories and assisting in the assimilation of those memories into long-term storage in other areas. It’s basically a place where all your memories go for a layover before continuing on to their final destination.

When Dr. Eagleman’s test subjects plummeted from the SCAD rig, their amygdalae ramped up and caused more information than normal to be retained after the fact. Most of the things you experience aren’t filed away for later — they’re just discarded. That’s not true when you are in danger — the brain keeps everything. When you think back on the event, you find a lot more information from that quarter of a second than you would expect, so it seems to have taken a longer time.

So your brain isn’t trying to give you an edge by slowing time when things go wrong. It’s just trying to teach you a lesson by keeping as much data on the danger as possible in hopes you’ll know better next time.

Eagleman believes this same retrospective perception of time is what makes the years seem to speed up as you grow older. As a child you’re forming rich memories with all manner of new experiences. As you get on in years, there is less new data to record, so fewer memories are formed. Looking back, there’s more data from youth, so your golden years seem short by comparison.

You’re always relying on memory when you try to assess what something was like as it happened. It’s just that squishy human brain playing tricks on you.